title: Fabrication, characterization, and functionalization of dual carbon electrodes as probes for scanning electrochemical microscopy (SECM).
abstract: Dual carbon electrodes (DCEs) are quickly, easily, and cheaply fabricated by depositing pyrolytic carbon into a quartz theta nanopipet. The size of DCEs can be controlled by adjusting the pulling parameters used to make the nanopipet. When operated in generation/collection (G/C) mode, the small separation between the electrodes leads to reasonable collection efficiencies of ca. 30%. A three-dimensional finite element method (FEM) simulation is developed to predict the current response of these electrodes as a means of estimating the probe geometry. Voltammetric measurements at individual electrodes combined with generation/collection measurements provide a reasonable guide to the electrode size. DCEs are employed in a scanning electrochemical microscopy (SECM) configuration, and their use for both approach curves and imaging is considered. G/C approach curve measurements are shown to be particularly sensitive to the nature of the substrate, with insulating surfaces leading to enhanced collection efficiencies, whereas conducting surfaces lead to a decrease of collection efficiency. As a proof-of-concept, DCEs are further used to locally generate an artificial electron acceptor and to follow the flux of this species and its reduced form during photosynthesis at isolated thylakoid membranes. In addition, 2-dimensional images of a single thylakoid membrane are reported and analyzed to demonstrate the high sensitivity of G/C measurements to localized surface processes. It is finally shown that individual nanometer-size electrodes can be functionalized through the selective deposition of platinum on one of the two electrodes in a DCE while leaving the other one unmodified. This provides an indication of the future versatility of this type of probe for nanoscale measurements and imaging.
authors.affiliation: Molecular Organisation and Assembly in Cells (MOAC) Doctoral Training Centre, School of Life Sciences, University of Warwick, Coventry, UK.
authors.forename: Kim
authors.initials: K
authors.lastname: McKelvey
authors.forename: Binoy Paulose
authors.initials: BP
authors.lastname: Nadappuram
authors.forename: Paolo
authors.initials: P
authors.lastname: Actis
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Yuri E
authors.initials: YE
authors.lastname: Korchev
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Matsue
authors.forename: Colin
authors.initials: C
authors.lastname: Robinson
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Unwin
mesh_terms: D002244:Carbon / Q000737:chemistry*; D004566:Electrodes; D064347:Microscopy, Electrochemical, Scanning / Q000295:instrumentation*; D057054:Molecular Imaging; D036103:Nanotechnology; D011791:Quartz / Q000737:chemistry; D020524:Thylakoids / Q000378:metabolism
chemical_list: C009139:pyrolytic carbon; D011791:Quartz; D002244:Carbon